KR101245950B1 - Back light unit and liquid crystal display device having thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit, and more particularly, to a backlight unit improving a lamp driving characteristic by minimizing the deviation of left and right tube currents of a lamp and a liquid crystal display device having the same. The disclosed invention is a plurality of lamps; An integrated inverter printed circuit board in which a master inverter and a slave inverter supplying power to the plurality of lamps are integrally formed; And first correction means and second correction means disposed between the master inverter and the lamp and the slave inverter and the lamp to correct the tube current deviation of both sides of the lamp, respectively.

The present invention has the effect of integrating the master inverter PCB and the slave inverter PCB to improve the assembly, and reduce the production cost.

LCD, lamp, inverter, correction means, impedance, tube current

Description

BACK LIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THEREOF}

1 is a view showing a state in which the inverter PCB according to the prior art is fastened to the bottom cover bottom of the liquid crystal display device.

2 is a view showing a state in which the integrated inverter PCB according to the present invention is fastened to the bottom cover bottom of the liquid crystal display device.

3 is a view showing an inverter structure according to the present invention.

4 is a view for explaining the principle of correcting the current deviation applied to the lamp from the master and the slave in the inverter of the present invention.

5 is a graph showing the current flowing in the master and the slave according to the size of the correction capacitor in the inverter according to the present invention.

6 is a table illustrating the graph of FIG. 5.

7 is a diagram illustrating the structure of an inverter according to another embodiment of the present invention.

Description of the Related Art [0002]

201: master inverter 202: slave inverter

220: lamp 240: protection circuit

250: main controller 261: first drive unit

262: first transformer 263: first feedback circuit

265: first correction means 275: second correction means

365: first inductance 375: second inductance

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit, and more particularly, to a backlight unit having a lamp driving characteristic improved by minimizing the deviation of left and right tube currents of a lamp and a liquid crystal display device having the same.

CRT (Cathode Ray Tube), one of the commonly used display devices, is mainly used for monitors such as TVs, measuring devices, and information terminal devices.However, due to the weight and size of the CRT itself, Could not respond actively to demands.

Therefore, in the trend of miniaturization and weight reduction of various electronic products, CRT has a certain limit in weight and size, and is expected to replace the liquid crystal display (LCD) and gas using an electro-optic effect. Plasma display panels (PDPs) using discharge and EL display elements (ELDs) using electroluminescent effects are among them, and among them, researches on liquid crystal displays have been actively conducted.

In order to replace the CRT, a liquid crystal display device having advantages such as small size, light weight, and low power consumption has been actively developed, and recently, the monitor of a laptop computer has been developed enough to perform a role as a flat panel display device. In addition, the demand for liquid crystal display devices continues to increase as they are used in monitors and large information display devices of desktop computers.

Since most of the liquid crystal display devices are light-receiving devices that display an image by controlling the amount of light coming from the outside, a separate light source for irradiating light to the LCD panel, that is, a backlight unit is required. .

Generally, a backlight unit used as a light source of a liquid crystal display device is a method of disposing a cylindrical light emitting lamp, and is divided into an edge method and a direct method.

In the double edge type, a lamp unit is installed on the side of a light guide plate for guiding light. The lamp unit includes a lamp that emits light, a lamp holder that is inserted at both ends of the lamp to protect the lamp, And a lamp reflector that is fitted to the side surface of the light guide plate and reflects the light emitted from the lamp toward the light guide plate.

As such, the edge method in which the lamp unit is installed on the side of the light guide plate is mainly applied to a liquid crystal display device having a relatively small size, such as a monitor of a laptop computer and a desktop computer, and has good light uniformity and a long durability life. It is advantageous to thin the liquid crystal display device.

On the other hand, the direct type method has been developed mainly as the size of the liquid crystal display device has increased to 20 inches or more, and a plurality of lamps are arranged in a row on the lower surface of the diffuser plate to direct light directly to the front of the LCD panel. will be.

The direct method is mainly used for a large screen liquid crystal display device requiring high luminance because the light utilization efficiency is higher than that of the edge method.

1 is a view showing a state in which the inverter PCB according to the prior art is fastened to the bottom cover bottom of the liquid crystal display device.

1, the master inverter PCB 30 for supplying power to the lamps on the back of the lower cover 10, the liquid crystal panel, the optical sheet and a plurality of lamps (not shown) disposed on the front and The slave inverter PCB 40 is disposed.

As described above, the master inverter PCB 30 and the slave inverter PCB 40 respectively supply high-voltage voltages having different phases to the lamps. EEFL (External Electrode Fluorescent Lamp).

The lamps are connected in parallel to a power terminal for receiving a voltage from the master inverter PCB 30 and a power terminal for receiving a voltage from the slave inverter PCB 40 at predetermined intervals.

Between the master inverter PCB 30 and the slave inverter PCB 40 receives a gating synchronization signal from the main controller to simultaneously synchronize the voltage generated by the master inverter PCB 30 with the voltage generated by the slave inverter PCB 40. Let's do it. Therefore, a cable 45 for synchronizing voltages is connected between the master inverter PCB 30 and the slave inverter PCB 40.

The conventional inverter having the above structure has the following problems.

First, since the main controller and the inverter protection circuit is further mounted on the master inverter PCB 30, the size is larger than that of the slave inverter PCB 40, so that the master inverter PCB and the slave inverter PCB process at the time of mounting the PCB It must be processed by dualizing, and it is difficult to work or assembly process because it needs to be assembled separately when assembling the backlight unit.

Second, since the master inverter PCB 30 and the slave inverter PCB 40 are spaced apart, there is a limit in reducing the production cost because additional synchronization cable for sending and receiving signals is required.

Third, since the control board, the master inverter PCB 30 and the slave inverter PCB 40 occupy a high portion of the lower cover rear surface of the liquid crystal display, they are spatially limited in arranging a power supply on the set.

SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight unit and a liquid crystal display device having the same, in which the master inverter PCB and the slave inverter PCB are integrated to improve assembling and reduce production costs.

Another object of the present invention is to provide a backlight unit and a liquid crystal display device having the same by integrating a master inverter PCB and a slave inverter PCB, thereby improving driving characteristics of a lamp by reducing a variation in lamp tube current generated.

According to an aspect of the present invention, there is provided a backlight unit comprising:

A plurality of lamps;

An integrated inverter printed circuit board in which a master inverter and a slave inverter supplying power to the plurality of lamps are integrally formed; And

And a first correction means and a second correction means disposed between the master inverter and the lamp and the slave inverter and the lamp, respectively, to correct the tube current deviation of both sides of the lamp.

According to another embodiment of the present invention,

A liquid crystal panel;

A plurality of lamps;

An integrated inverter printed circuit board in which a master inverter and a slave inverter which apply power to both ends of the plurality of lamps are integrally formed; And

And a first correction means and a second correction means disposed between the master inverter and the lamp and the slave inverter and the lamp, respectively, to correct the tube current deviation of both sides of the lamp.

According to the present invention, the master inverter PCB and the slave inverter PCB are integrated to improve the assembly and reduce the production cost.

In addition, by integrating the master inverter PCB and the slave inverter PCB, the generated lamp tube current deviation is reduced to improve the driving characteristics of the lamp.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a view showing a state in which the integrated inverter PCB according to the present invention is fastened to the bottom cover bottom of the liquid crystal display device, Figure 3 is a view showing the structure of the inverter according to the present invention.

As shown in FIGS. 2 and 3, an integrated inverter PCB 200 is disposed on the rear surface of the lower cover 150 of the liquid crystal display, and the master inverter 201 and the slave inverter are inside the integrated inverter PCB 200. 202 is mounted together.

The integrated inverter PCB 200 is usually disposed at one side edge area of the rear surface of the lower cover 150. In addition, in the master inverter 201 and the slave inverter 202, the first lamp wire 180a and the second lamp wire 180b are drawn out to supply a voltage to the lamp 220 (see FIG. 3).

The first lamp wire 180a drawn out from the master inverter 201 is connected to one power terminal of lamps (not shown) disposed inside the lower cover 150 and drawn out from the slave inverter 202. The second lamp wire 180b is connected to the other power terminal of the lamps.

As such, by mounting the master inverter 201 and the slave inverter 202 on one integrated inverter PCB 200, there is no need to separately use a synchronous cable between the master inverter 201 and the slave inverter 202. . That is, the master inverter 201 and the slave inverter 202 may be synchronized by patterning wires on the integrated inverter PCB 200.

However, when the integrated inverter PCB 200 in which the master inverter 201 and the slave inverter 202 are integrally formed is disposed in one corner area of the rear surface of the lower cover 150, the master inverter 201 or the slave inverter 202 may be used. Either one of the lamp wires 180a and 180b drawn out from it should be formed long.

As shown in the figure, the second lamp wire 180b withdrawn from the slave inverter 202 is longer than the first lamp wire 180a withdrawn from the master inverter 201, and the second lamp wire 180b has a lower cover. Along the back of the 150 is disposed in the opposite direction in which the integrated inverter PCB 200 is located.

Therefore, the parasitic capacitance formed between the first lamp wire 180a and the bottom cover 150 is greater than the parasitic capacitance formed between the second lamp wire 180b and the bottom cover 150. The leakage current in the region of the second lamp wire 180b is large.

As described above, the tube current deviation occurs on both sides of the lamp due to the difference in parasitic capacitance and is applied as a cause of deterioration of the lamp driving characteristic.

In order to solve the above problems, in the present invention, the master inverter 201 and the slave inverter 202 are formed on the integrated inverter PCB 200, and then the lamp 220 is applied to the master inverter 201 and the slave inverter 202. The first correcting means 265 and the second correcting means 275 are disposed to adjust the current deviation applied to.

In the inverter configuration of the present invention, a plurality of lamps 220 arranged at regular intervals, and the master inverter (master 201) and the slave inverter (slave) (202) for applying a driving voltage to both sides of the lamp 220 The main controller 250 controls the master inverter 201 and the slave inverter 202 and a protection circuit 240 protecting the inverter.

The master inverter 201 includes a first driver 261 composed of a field effect transistor (FET) and a first transformer for converting current output from the first driver 261 into a voltage for supplying the lamp 220 ( transformer 262 and a first feedback circuit 263 for feeding back the waveform of the first transformer 262 to adjust the inverter.

The slave inverter 202 may correspond to the first driver 261, the first transformer 262, and the first feedback circuit 263 of the master inverter 201, and the second transformer 271 and the second transformer 272. ), And a second feedback circuit 273.

Further, in the present invention, the first correction means 265 for current deviation correction is disposed between the output terminal of the first transformer 262 and the lamp 220, the output terminal and the lamp ( First correction means 275 for current deviation correction is also disposed between the 220.

The first correcting means 265 and the second correcting means 275 use a variable capacitor.

Therefore, the length of the first lamp wire 180a drawn out from the master inverter 201 and the second lamp wire 180b drawn out from the slave inverter 202 are compared to increase the capacitance of the variable capacitor at the shorter length and length. To make the capacity of the variable capacitor smaller on the longer side.

This is because, when the length of the lamp wire is long, the parasitic capacitor generated between the rear surface of the lower cover 150 is large, so that more current leakage occurs than the side of the lamp wire having a small length.

As described above, in the present invention, by adjusting the capacitor capacitance of the first correction means 265 and the second correction means 275, the tube current flowing to both sides of the lamp 220 may be the same.

As described above, the principle of controlling the tube current flowing to both sides of the lamp 220 by adjusting the capacitor capacities of the first correcting means 265 and the second correcting means 275 is the master inverter 201 at both ends of the lamp 220. And by controlling the impedances facing the direction of the slave inverter 202 to be the same.

4 is a view for explaining the principle of correcting the current deviation applied to the lamp from the master and the slave in the inverter of the present invention.

As shown in FIG. 4, a capacitor detecting an abnormal driving voltage for protecting the inverter is connected in series between the output terminal of the first transformer 262 of the master inverter and the lamp 220.

Correspondingly, a capacitor detecting an abnormal driving voltage for protecting the inverter is connected in series between the output terminal of the second transformer 272 of the slave inverter and the lamp 220.

Therefore, the output terminal of the first transformer 262 and the output terminal of the second transformer 272 are connected to the protection circuit 240 to shut down the inverter when a high voltage is applied to the lamp 220 or no voltage is applied. Protect it.

In addition, a first feedback circuit 263 and a second feedback circuit 273 are connected to each other so as to measure a current value from the ground terminals of the first transformer 262 and the second transformer 272, respectively. 262 and the output voltage of the second transformer 272 is controlled.

In the present invention, the first correction means (265: CR1) and the second correction means for correcting the current deviation between the first transformer 262 and the lamp 220, the second transformer 272 and the lamp 220 ( 275: CR2).

The first lamp wire 180a connected to the output terminal of the first transformer 262 and the lamp 220 is short, and the second lamp wire 180b connected to the output terminal of the second transformer 272 and the lamp 220 is As long as the parasitic capacitances Cst1 and Cst2 are large in the region of the second lamp wire 180b.

Therefore, the capacitor capacity of the first correction means 265 is increased and the capacitor capacity of the second correction means 275 is made smaller, so that the current flowing through the first lamp wire 180a and the second lamp wire 180b has the same value. Will have

That is, the parasitic capacitance generated between the capacitor value CR1 of the first correction means 265 on the master inverter side and the capacitor value CR2 of the second correction means 275 on the slave inverter side, and the second lamp wire 180b and the lower cover. If the sum of Cst1, Cst2, ... is the same, the currents on both sides of the lamp 220 have the same value (because the leakage currents are the same because the capacitors are the same size).

This can also be said to have the same impedance seen across the lamp 220 to the master inverter area and the slave inverter area, so when the same voltage is applied across the lamp 22, the lamp 220 has the same impedance. The same tube current flows through it.

FIG. 5 is a graph illustrating a current flowing through a master and a slave according to the size of a correction capacitor in an inverter according to the present invention, and FIG. 6 is a table illustrating the graph of FIG. 5.

As shown in FIG. 5 and FIG. 6, the capacitor capacity of the second correction means connected to the master inverter is varied in the region of 37 pF while the capacitor capacity of the second correction means connected to the slave inverter is fixed at 10 pF. It can be seen that the tube current across the lamp is almost the same.

If the value of the capacitor of the first correction means connected to the master inverter approaches the value of the capacitor of the second correction means connected to the slave inverter, it can be seen that the tube current deviation generated at both ends of the lamp increases very much. (Master 22 [pF], Slave 10 [pF])

The graph and table illustrate an example in which a lamp wire connected to a master inverter is short and a lamp wire connected to a slave inverter is long.

Accordingly, when the lamp wire connected to the master inverter is long and the lamp wire connected to the slave inverter is short, the capacitor value of the second correction means is made larger than the capacitor value of the first correction means.

7 is a diagram illustrating the structure of an inverter according to another embodiment of the present invention.

FIG. 7 illustrates a first inductance 365 connected to an output terminal of the first transformer 262 and a second inductance 375 to an output terminal of the second transformer 272 in order to adjust a current variation flowing across the lamp 220. ), Respectively.

Therefore, reference numerals of the drawings that are not described refer to FIG. 4.

Since the voltages applied from the first transformer 262 and the second transformer 272 to the lamp 220 have only the phase difference and have the same HIGH-HIGH voltage, the first transformer 262 at both ends of the lamp 220 are respectively. ) And the inductance value was adjusted to equalize the impedance viewed from the second transformer 272.

Particularly, when the first inductance 365 and the second inductance 375 resonate with the capacitance generated on the first transformer 262 and the capacitance generated on the second transformer 272, the impedance according to the relation of impedance Only the resistance component remains so that the tube current at both ends of the lamp 220 is the same.

Therefore, the first inductance 365 may be connected in series and in parallel with the first correction means 265. In addition, the first inductance 365 may be adjusted to an inductance value between the secondary windings of the first transformer 262 or the material of the windings.

에 따라 공진 주파수

를 적절히 맞출 수 있어 램프(220) 양단의 임피던스 크기를 조절할 수 있다.When adjusting the inductance like this,

According to the resonant frequency

Can be appropriately adjusted so that the impedance of both ends of the lamp 220 can be adjusted.

Similarly, the second inductance 375 may be connected in series or in parallel with the second correction means 275, or may adjust the inductance value by adjusting the material of the windings or between the secondary windings of the second transformer 272. .

As described above, the impedance viewed from both ends of the lamp 220 may be adjusted using the inductance, or the impedance may be adjusted by connecting the first correction means 265 and the second correction means 275 together.

As such, there is an advantage in that the tube current deviation generated at both ends of the lamp can be minimized by adjusting the capacitance or inductance at both ends of the lamp 220.

As described in detail above, the present invention has the effect of integrating the master inverter PCB and the slave inverter PCB to improve the assembly and reduce the production cost.

In addition, by integrating the master inverter PCB and the slave inverter PCB, there is an effect of reducing the lamp tube current deviation generated to improve the driving characteristics of the lamp.

The present invention is not limited to the above-described embodiments, and various changes can be made by those skilled in the art without departing from the gist of the present invention as claimed in the following claims.

Claims (10)

A plurality of lamps; An integrated inverter printed circuit board in which a master inverter and a slave inverter supplying power to the plurality of lamps are integrally formed; First and second correction means disposed between the master inverter and the lamp and the slave inverter and the lamp to correct the tube current deviation of both sides of the lamp, respectively; And And a first inductance and a second inductance respectively disposed to correct the tube current deviation of both lamps between the master inverter and the lamp and the slave inverter and the lamp. 2. The backlight unit of claim 1, wherein the first correcting means and the second correcting means are variable capacitors, respectively. The backlight unit of claim 2, wherein the variable capacitors of the first correcting means and the second correcting means have the same capacitance between the master inverter and the lamp and the capacitance between the slave inverter and the lamp. . delete The backlight unit of claim 1, wherein the first inductance and the second inductance are adjusted to have the same impedance as viewed at the master inverter and the slave inverter at both ends of a lamp. A liquid crystal panel; A plurality of lamps; An integrated inverter printed circuit board in which a master inverter and a slave inverter which apply power to both ends of the plurality of lamps are integrally formed; First and second correction means disposed between the master inverter and the lamp and the slave inverter and the lamp to correct the tube current deviation of both sides of the lamp, respectively; And And a first inductance and a second inductance, respectively, disposed between the master inverter and the lamp and the slave inverter and the lamp to correct the tube current deviation of both sides of the lamp. 7. The liquid crystal display device according to claim 6, wherein the first correcting means and the second correcting means are variable capacitors, respectively. 8. The liquid crystal display of claim 7, wherein the variable capacitors of the first correcting means and the second correcting means have the same capacitance between the master inverter and the lamp and the capacitance between the slave inverter and the lamp. . delete 7. The liquid crystal display of claim 6, wherein the first inductance and the second inductance are adjusted to have the same impedance as viewed at the master inverter and the slave inverter at both ends of the lamp.

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